Efficient Dual-Band Rectifier Using Stepped Impedance Stub Matching Network for Wireless Energy Harvesting Li, S., Cheng, F., Gu, C., Yu, S., & Huang, K. (2021). Efficient Dual-Band Rectifier Using Stepped Impedance Stub Matching Network for Wireless Energy Harvesting. IEEE Microwave and Wireless Components Letters. https://doi.org/10.1109/LMWC.2021.3078546 Published in: IEEE Microwave and Wireless Components Letters Document Version: Peer reviewed version Queen's University Belfast - Research Portal: Link to publication record in Queen's University Belfast Research Portal Publisher rights © 2021 IEEE. This work is made available online in accordance with the publisher’s policies. Please refer to any applicable terms of use of the publisher. 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Sep. 2021 Page 1 of 4 > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Efficient Dual-band Rectifier Using Stepped Impedance Stub Matching Network for Wireless Energy Harvesting Shun Li, Fei Cheng, Chao Gu, Sha Yu, and Kama Huang, Senior Member, IEEE The mobile communications and wifi networks usually pro- Abstract—This letter presents an efficient dual-band rectifier vide the radiation sources for WEH. Thus, the desired fre- using stepped impedance stub matching circuit. Theoretical anal- quencies for dual-band rectifiers are 900, 1800 and 2100 MHz ysis of the dual-band impedance matching circuit comprised of a for mobile communications, as well as 915, 2450 and 5800 stepped impedance stub is carried out which plays a key role in designing the resultant dual-band rectifier. The proposed du- MHz for ISM band applications. Compared with a dual-band al-band matching circuit can achieve wide frequency ratio which is rectifier, the broadband rectifier can cover more bands and analyzed and predicted by simulation. For demonstration, a du- harvest more energy. However, it usually has a no more than one al-band rectifier working at 0.915 and 2.45 GHz is fabricated with octave bandwidth which cannot simultaneously cover 915 and dimensions of 21.47 mm× 18.93 mm. The measured results show 2450 MHz bands [8]-[11]. The dual-band rectifier can com- that with a 1500 Ω load, the maximum efficiencies of the rectifier pensate this drawback due to the fact that it is easier to achieve a reach 74% and 73% at 0.915 and 2.45 GHz, respectively. Due to the simple but efficient structure of the dual-band matching net- large frequency ratio including 915/2450 MHz [12]-[14]. work, the dual-band rectifier in this work exhibits merits of The key point for a dual-band rectifier design is the dual-band compact size and high efficiency. input matching network. In the previous works, single-stage T-type network [12], two stage T-type networks [16], multi-stub Index Terms—Wireless energy harvesting, dual-band, high ef- networks [14, 15, 17-20], coupled lines [13], and LC networks ficiency, rectifier, impedance matching, stepped impedance stub. [21, 22] have been used as the dual-band matching network in the rectifier circuit design. Most of the designs have more than three segments of transmission lines in the matching network I. INTRODUCTION which results in large circuit size and complex design [13]-[20]. he wireless energy harvesting technology (WEH) is a The LC matching networks can minimize the circuit size [21, Tpromising technology which can power some low power 22]. But the low Q capacitors and inductors would lead to electrical systems including the wireless communication sys- higher loss and lower efficiency of the rectifier compared with tems and wireless sensor networks without wires [1]-[4]. WEH the transmission line networks. aims to collect wasted energy from the ambient environment, so In this letter, an efficient dual-band rectifier using a stepped it is a promising solution of reducing pollution when employed impedance stub matching network is proposed for wireless in battery less low-power sensors. The microwave rectifier is a energy harvesting application. The traditional single-stub im- key component in a wireless energy harvesting system because pedance matching network only can achieve a single band the conversion from the received microwave power to the usa- matching performance [7]. In this work, the uniform impedance ble DC supply is directly affected by the rectifier. In the past single-stub is replaced by stepped impedance stub to achieve years, many single band rectifiers have been proposed for WEH dual-band performance. We first demonstrate in the simulation applications [5]-[7]. Compared with a single band rectifier, that by controlling the impedance and length of the stepped broadband [8]-[11], dual-band [12]-[22] and multi-band recti- impedance stub matching network, the frequency ratio of the fiers [23]-[26] can harvest microwave energy in more bands two working frequency bands can be adjusted and large fre- thus producing more DC energy. Consequently, quency ratio of 3.77 (650 and 2450 MHz) can be achieved. To broad/multi-band rectifiers have attracted growing attentions in verify the design concept, a dual-band rectifier working at 0.915 recent years. and 2.45 GHz is fabricated and measured. The resulting rectifier uses only three microstrip lines in the matching network which is less than those in the previous works [13]-[20]. So it releases This work was supported by the National Natural Science Foundation of the design complexity and exhibits compact size. The measured China under project number 61801317. (Corresponding author: Fei Cheng) results of the rectifier agree well with the simulated results. The Shun Li, Fei Cheng, Sha Yu and Kama Huang are with College of Elec- tronics and Information Engineering, Sichuan University, Chengdu, 610065, measured |S11| is better than -20 dB at the two operating bands China. (E-mail: [email protected]) and the peak conversion efficiencies are 74% and 73% at 0.915 Chao Gu is with Centre for Wireless Innovation, ECIT Institute, Queens and 2.45 GHz, respectively. University Belfast, Belfast, BT3 9DT, UK. (E-mail: [email protected]) Page 2 of 4 > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 2 II. DESIGN AND ANALYSIS OF THE DUAL-BAND RECTIFIER Yin f i Y in1 f i Y stub f i 1, i =1, 2. (2) The block diagram of the proposed dual-band rectifier which Then, the input impedance of the rectifier is matched at two works at f1 and f2 is shown in Fig. 1. It consists of a single-stub frequencies. impedance matching network, a Schottky diode, and a DC pass B. Design of the dual-band rectifiers with different fre- filter. In the single-stub impedance matching network, the quency ratios shorted stepped impedance stub comprised of TL3 and TL4 can 0 not only achieve dual-band matching, but also provide DC 80 -10 ground for the rectifier. Zi and θi represent the characteristic 60 impedance and electrical length of the ith microstrip transmis- 40 -20 PCE (%) sion line at f1 (i = 1, 2, 3, 4). The single-series topology is chosen B C D (dB) |S11| here to eliminate the use of an input DC block capacitor re- 20 A -30 quired in the single-parallel topology. Thus, the loss of the DC 0 block capacitor can be eliminated to enhance the rectifier effi- 0.5 1.0 1.5 2.0 2.5 3.0 Frequency (GHz) ciency. Fig. 3. Simulated |S11| and PCE versus frequency for dual-band rectifiers of 4 frequency ratios. (Dash line: |S11|, solid line: PCE) TABLE I PARAMETERS FOR THE DUAL-BAND RECTIFIERS OF 4 FREQUENCY RATIOS Model Z1 Z2 Z3 Z4 θ1 θ2 θ3 θ4 A 51.9 76.1 46.1 30 80.3 282.5 52.4 45.8 B 94.1 97.6 39.8 85.2 66.2 188.1 37.7 22.6 C 95.7 92.4 61.2 37.7 75.9 103.1 25.5 30.7 D 103.2 49.6 98.1 99.6 73.9 82.4 3.8 11.5 Unit: Ω (characteristic impedance) and degree (electrical length @ 2.45 GHz) The proposed input impedance matching network design is Fig. 1. Schematic of the proposed dual-band rectifier. valid for dual-band operation with different frequency ratios. In A. Analysis of the dual-band matching network order to validate it, dual-band rectifiers with 4 different fre- quency ratios are simulated in ADS. The higher frequency of the rectifiers is fixed at 2.45 GHz while the lower frequency is adjusted at 0.65, 0.915, 1.45, and 1.8 GHz for model A, B, C and D. The corresponding frequency ratios are 3.77, 2.68, 1.69, and 1.36, respectively. In the simulation, the Infineon BAT15-03W Schottky diode is used and it has a series re- sistance of 5 Ω and zero-bias junction capacitance of 138.5 fF. The original breakdown voltage of the diode in the datasheet is 4.2 V.